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There were actually two large rebel groups, led respectively by Li Zicheng and Zhang Xianzhong. It was the former which led his rebel army into Beijing with the Chongzhen Emperor hanging himself on 4/25/1644. Li proclaimed himself emperor of the new Shun dynasty. Prior to his arrival in Beijing, a Ming army garrisoning the northern frontier (to guard against the Manchu) was recalled to help defend the Ming capital. That army was led by a general by the name of Wu Sangui. Wu's army did not arrive in time to stop Beijing from falling to Li. Additionally it turned out that Wu's father was a Ming official in Beijing. Further Wu's father wound up being killed by Li's forces (some sources also claim Li held Wu's mistress as a hostage in Beijing, but there is disagreement on this point). At any rate with Wu's forces off the frontier, the Manchu advanced south under Prince Dorgon. Wu thus found himself sandwiched between the Manchu and Li. Wu decided to ally with the Manchu to defeat Li. The two sides (Li vs. Wu/Dorgon) fought at the battle of Shanhaiguan in May 1644 with each having about 100,000 men. Li was completely defeated and the Qing dynasty thus rose to power, with the Shun dynasty having lasted less than a month. The following year the Qing would rout Zhang Xianzhong's army in Sichuan province. The remnants of the Ming hierarchy would splinter to flee to the southwest and southeast. In the southwest, the last descendant of the Ming emperor, Yongli, was hunted down by Wu Sangui in Yunnan province in 1661. In the southeast fleeing Ming forces would last longer. Led by Zheng Chenggong, rallied Ming loyalists advanced as far north as Nanjing before being defeated by the Qing. Zheng then fled to Taiwan where in 1661 he defeated the Dutch who held the island (the Dutch called him Koxinga an approximate form of Zheng's original name Kuo Hsing Yeh). Eventually the Qing were able to restablish control over the island in 1683. If that weren't enough, Wu Sangui was to play a leading role in the Revolt of the Three Feudatories (1674-1683). One wonders if Wu's later revolt against the Ming is evidence that he had regrets about joining with the Manchu rather than with Li Zicheng back in 1644.